CaptchaValidator.cs

public class CaptchaValidator : ICaptchaValidator
    {
        private readonly HttpClient _httpClient;

        public CaptchaValidator(HttpClient httpClient)
        {
            _httpClient = httpClient;
        }

        public async Task<CaptchaResponse> ValidateCaptchaAsync()
        {
            _httpClient.BaseAddress = new Uri("https://www.google.com/");
            _httpClient.DefaultRequestHeaders.Accept.Clear();
            _httpClient.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));

            HttpResponseMessage response = await _httpClient.GetAsync($"recaptcha/api/siteverify");
        }
}